1. Technical Field
This invention relates to the reduction of fogging of medical device lenses. More particularly, compositions and methods for reducing and inhibiting fogging of endoscope lenses are disclosed.
2. Description of Related Art
It is desirable to eliminate the formation of fog or moisture on transparent or reflecting surfaces such as glass and plastic materials. This is particularly true for medical instrument lenses used during diagnostic and surgical procedures. Endoscopes provide medical diagnosis and treatment at relatively inaccessible and remote locations within a body. Endoscope lenses are prone to fogging due to ambient temperature changes. When an endoscope is inserted into a human body, fog or fine water droplets adhere to the lens due to the cooling of water vapor in the body cavity when the endoscope having a temperature of the ambient atmosphere is introduced to the body cavity having a higher temperature of about 36.degree. C. and 100% humidity.
During an endoscopic procedure, the temperature of the lens gradually increases to the temperature of the body cavity. However, it is sometimes necessary to supply water or air to the body cavity. The addition of water or air to the body cavity lowers the temperature of the endoscope lens which also contributes to fogging of the lens.
Fogging of the endoscope lens obstructs the endoscope operator's view. The view through the endoscope lens generally becomes blurred or "smokey" due to the fogging. Consequently, the length of time required for completing endoscopic procedures is greatly increased. This is extremely disadvantageous for both the operator and the patient undergoing the endoscopic procedure. Furthermore, fogging of endoscopic lenses interferes with endoscopic photography and video endoscopy.
Certain attempts have been made to reduce or eliminate fogging of transparent or reflecting surfaces such as glass, lenses, contact lenses, eyeglasses, goggles, diving masks, mirrors, and plastic food wrapping material. A number of antifogging polymeric coatings, films, and solutions are known in the art, including acrylate-based polymers (see, for example, U.S. Pat. Nos. 3,515,579, 3,865,619 and 3,900,672) and organosiloxane-oxyalkylene block copolymers (see U.S. Pat. No. 3,933,407). Other antifogging compositions include polyethoxy alcohol, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene esters or ethers, polymeric vinyl films, polyvinyl alcohol, polyalkylene imine polymer and block copolymers of polyurethane and hydrophilic copolyacrylics. (See U.S. Pat. Nos. 2,803,552, 2,726,962, 3,048,266, 4,964,308, 3,935,367, 3,950,289, 4,242,412 and 5,180,760.)
Certain apparatuses and methods specifically designed for cleaning endoscope lenses are also known in the art. Modifications to endoscopic instruments such as endoscopic lens wiper devices and lens adapters have been employed for eliminating materials and fog from lenses. (See U.S. Pat. Nos. 3,145,249 and 5,125,394.) Other methods include the application of air having the same temperature as the ambient atmosphere over the surface of an endoscope lens to stabilize the temperature of the lens while it is inside a body. (See U.S. Pat. No. 4,497,500.) U.S. Pat. No. 3,924,608 describes an endoscope having a suction port for removing liquid from the outer surface of the distal endoscope observation lens.
Many prior methods for eliminating fog or other materials from endoscope lenses are time consuming and increase the risk of infection because they require removal of the endoscope from the body. In these methods, once fog develops on the endoscope lens, the endoscope is removed from the body cavity, and antifogging compositions are applied to the lens with a sponge. A dry sponge is then used to wipe away any unevaporated composition from the endoscope lens. The endoscope is then reinserted into the body to continue the procedure. Methods for cleaning endoscopic lenses by applying liquid or gas directly to the endoscope lens during an endoscopic procedure overcome the drawbacks of methods which require removal of the endoscope from a body to clean it. A liquid or gas is delivered through an outlet or nozzle at the distal end of the endoscope during the endoscopic procedure. (See U.S. Pat. Nos. 3,980,078, 4,281,646, 4,844,052, 4,548,197 5,022,382 and 5,133,336.) However, where liquid is applied to an endoscopic lens during a procedure it is often necessary to vigorously remove nonbiocompatible liquids from the body cavity by aspiration in order to avoid adverse side effects.
While polyoxyalkylenes have been used as a component in solutions designed for cleaning and wetting contact lenses (see U.S. Pat. Nos. 3,954,644, 3,882,036, 4,046,706, 4,440,662, 4,510,065, 4,543,200 and 4,613,380), polyoxyalkylene solutions have not been used to reduce or eliminate fog on endoscope lenses while the endoscope remains within the body.
An efficient and safe method for eliminating fog from endoscope lenses during endoscopic procedures which does not require removal of the endoscope from the body cavity and which employs only biocompatible materials would be desirable.